The site of protein synthesis in a cell is primarily the ribosome. Ribosomes are complex molecular machines found within all living cells, and they play a crucial role in translating messenger RNA (mRNA) into polypeptides, which then fold into active proteins.
During protein synthesis, the ribosome reads the sequence of mRNA and assembles amino acids in the correct order to create a specific protein. This process involves two main stages: transcription, where the DNA sequence is copied to mRNA, and translation, where the ribosome translates the mRNA sequence into a protein.
Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum (ER), specifically the rough ER, which is involved in the production of proteins that are either secreted from the cell or incorporated into cellular membranes. The ribosomes on the rough ER help synthesize proteins that are meant for secretion, while those in the cytoplasm generally produce proteins that function within the cell itself.